Tuna niçoise

Place an egg in a pan of cold water. Cover and bring to the boil. Boil for 5 minutes, then drain and cool under cold water. Set aside. Meanwhile, add the potato to a pan of boiling water and bring back to the boil. Simmer, uncovered, for 15 minutes adding the green beans for the final 5 minutes. Drain and cool under cold running water. Tear the lettuce leaves into pieces and place in a salad bowl. Add the potato, green beans, tomatoes, basil and olives. Toss to mix. Scatter the tuna over the salad. Peel and slice the eggs and arrange them on top of the salad. Pour the olive oil, red wine vinegar and lemon juice in a screw-top jar and season. Tighten the lid and shake until combined. Drizzle over the salad and serve.